This invention relates to electroacoustic transducer assemblies and, more particularly, to a high efficiency electroacoustic transducer assembly using piezoelectric polymer material.
One use of electroacoustic transducer assemblies is as probes for certain types of ultrasonic medical diagnostic equipment. When used in such an application, water, rather than air, is typically interposed between the probe and the skin of the patient. This results in a reduction of the reflection of the ultrasonic waves by the skin over the situation where the ultrasonic waves are transmitted through air.
Piezoelectric polymer materials, such as polyvinylidene fluoride (PVDF) or polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) in film form, are known as relatively inexpensive and comformable materials that can be utilized in such ultrasonic electroacoustic transducer assemblies because their acoustic impedances are close to that of water, which minimizes boundary reflection. Although the frequency responses of such materials, both for transmitting and receiving, cover a much wider frequency band than those of ceramic piezoelectric materials, the magnitudes of generated waves are much weaker than those of ceramic piezoelectric materials. It is therefore a primary object of the present invention to provide an electroacoustic transducer assembly utilizing piezoelectric polymer film material which has increased efficiency.